The present invention relates to a decentration optical system using a rotationally asymmetrical surface, and an optical apparatus such as an image display apparatus and an imaging apparatus, each with such a decentration optical system incorporated inside.
So far, it has been known to use a prism having a plurality of optical surfaces as an optical system for viewing an image display device. In such a prism, light exiting out from the display device enters the prism. Then, the light is reflected within the prism, and leaves the prism, arriving at the viewer's eyeball so that an image may be viewed as an enlarged virtual image.
For such an image-viewing optical system, JP(A) 2008-76429 discloses a prism that forms a primary image by at least three reflective surfaces for projection onto the eyeball. JP(A)'s 2007-94175 and 2004-325985 disclose eyeglasses with a hologram device mounted on their lens segment.
For another optical system used on image display devices, JP(A) 2006-3879 discloses projecting light through a light guide and an eyepiece lens onto the eyeball. U.S. Pat. No. 3,924,348 discloses a decentration optical system in which a space surrounded by three surfaces is filled up with a medium having a refractive index of 1 or greater, and at least one surface is defined by a curved surface having no symmetrical plane. Two image display devices are so aligned in line that aberrations can be corrected even when, in a vergence layout, axial chief rays for the image display devices and the decentration optical system are located in a twisted manner.